1. Field of the Invention
The present invention relates to a source driver. More particularly, the present invention relates to a source driver for reducing power consumption thereof with a charge sharing function, and a driving method thereof.
2. Description of Related Art
In order to catch up with the modern lifestyle, video and image devices are becoming slimmer and lighter. Despite of advantages it may have, a conventional cathode-ray tube (CRT) display not only is large in bulk that occupies too much room because of its intrinsic structure of the electronic cavity, but also radiates rays which may hurt human eyes. Therefore, accompanying the development of optoelectronic technology and semi-conductor processing technology, flat panel displays including liquid crystal display (LCD), organic light-emitting diode (OLED) display and plasma display panel (PDP) are gradually becoming a mainstream in the display market.
Resolutions and refreshing frequencies of flat panel displays are continuously improving. Consequently, refreshing frequencies of scan lines are demanded to be more and more rapid, which contradicts the designs for power saving by system engineers. As a result, a technology for eliminating the contradiction therebetween called “smart charge sharing” technology is developed thereby.
FIGS. 1A and 1B are schematic diagrams of a conventional charge sharing technology. Referring to FIG. 1A, first, a display 100 includes a source driver 110 and a display panel 130. The display panel 130 includes a plurality of data lines DL1-DLm electrically connected to the source driver 110. The source driver 110 includes a plurality of data channels ch1-chm, and each of the data channels includes a corresponding output amplifier. For example, the data channel ch1 includes the output amplifier A1, the data channel ch2 includes the output amplifier A2, and so on. Each of the data channels is respectively connected to a corresponding data line through the output terminal of the corresponding output amplifier. The source driver 110 further includes a plurality of switches SW1-SWm-1 for connecting adjacent two data lines. For example, a switch SW1 is adapted for connecting the adjacent data lines DL1 and DL2. As shown in FIG. 1A, each data line is taken as a sum of loads of resistance and capacitance of a corresponding output amplifier.
FIG. 1C is a signal timing diagram of an even data line and an odd data line in FIG. 1B. Before the source driver 110 driving the display panel 130, voltages of each pair of the adjacent data lines (here the voltage V1 of the data line D1 and the voltage V2 of the data line D2 are used for illustration) are respectively higher and lower than a common voltage Vcom. Meanwhile, all of the switches SW1-SWm-1 are at turn-off status. At the instance that the source driver 110 starts to drive the display panel 130 in a charge sharing period t1, all of the switches SW1-SWm-1 will be switched to turn-on status as shown in FIG. 1B. At this certain instance, all amplifiers A1-Am are at disable status without current consumption. However, as the switches SW1-SWm-1 are at turn-on status, there will be a current flowing from a data line having a voltage higher than the common voltage Vcom to a data line having a voltage lower than the common voltage Vcom, the path of which is as illustrated of the arrowheads in FIG. 1B. Thus, charges can be neutralized therein. After that, the switches SW1-SWm-1 will go back to the turn-off status in a normal driving period t2, while the source driver 110 can drive the display panel 130 as usual. After the normal driving period t2 is end, the process proceeds to a charge sharing period t3, and the internal circuit of the display 100 begins to perform the charge sharing operation again, so as to repeatedly perform the same activity.
In summary, the principle of the charge sharing technology is to reallocate energy (charges) stored in the data lines and whereby to drive the data lines to a half of the final value without power consumption. However, while the display panel 130 is driven with column inversion method, the voltage V1′ of the data line D1 is not needed to swing lower than the common voltage Vcom in a frame, and in contrast, the voltage V2′ of the data line D2 is not needed to swing higher than the common voltage Vcom in the frame, either. FIG. 1D is a signal timing diagram of an even data line and an odd data line in FIG. 1B while the display panel 130 is driven with column inversion method. Therefore, such charge sharing technology is not suitable for the specific condition mentioned above. Because the swings of the voltages are much than desire, extra power is consumed. It is desirable to design a proper source driver to solve the said problem.